CEPI’s mission to accelerate vaccine development against infectious diseases is underpinned by an approach that explores the potential for a range of different vaccine technologies, all or any of which might be tailored to respond quickly and effectively to a future epidemic or pandemic threat.
By investing in research and development for multiple types of vaccine platform, such as viral vector, protein subunit and mRNA technologies, CEPI mitigates against the risk of relying on a single technology. This increases the likelihood of successfully developing safe and effective vaccines for both known epidemic threats and future novel ‘Disease X’ threats.
Using ‘Answer the Public’, we analysed some of the most popular search terms related to viral vector vaccines across the United States, the United Kingdom and South Korea, which were among the top countries searching ‘viral vector vaccines’ over the past 12 months, according to Google Trends at the time of publishing.
Below is a selection of those questions, with CEPI’s answers:
What is a viral vector vaccine?
Viral vector vaccines use a harmless version of a carrier virus, or vector, to deliver specific genetic instructions to human cells. Those instructions help the cells to make proteins known as antigens that can trigger an immune response against the potentially harmful disease-causing virus, teaching the body to recognise and fight it in future.
What kinds of viruses are used as vectors, and how do viral vector vaccines work?
Various viruses have been developed as vectors by being stripped of their disease-causing genes so that they are rendered harmless. Examples of vector viruses include adenoviruses—which, when live, are a cause of commons colds—as well as the vesicular stomatitis virus, or VSV.
The genetic instructions for making the antigen from the pathogen that the vaccine is designed to fight are embedded into the vector virus’s genome. When it is injected into the body via the vaccination, it carries those instructions into cells.
Inside the cell, the vector releases the genetic instructions for the cell to produce the antigen, which is then presented to the immune system, triggering an immune response. This teaches the body to recognise and fight the actual harmful virus carrying this same antigen if it encounters it again.
Are viral vector vaccines safe?
Yes. All regulator-approved viral vector vaccines—for example those against diseases such as Ebola and COVID-19—have been extensively tested in multiple clinical trials across the world. Viral vector vaccines are built on well-established science, with decades of research supporting their development. The first viral vector vaccines date back to the early 1970s and, to date, millions of people worldwide have received them. As part of established processes for monitoring of licensed medicines, the safety and effectiveness of these vaccines continues to be monitored by regulators around the world.
Can viral vector vaccines have side effects?
All vaccines and medicines can have side effects, but serious side effects are extremely rare and far outweighed by the risks of the diseases they are designed to protect against.
Because viral vector vaccines cause a strong immune response, minor, short-term post-vaccination side effects such as headache and fever can be more common than with other types of vaccine.
Two viral vector vaccines against COVID-19, one developed by Johnson & Johnson and another developed by AstraZeneca and Oxford University, have been linked to a very rare clotting disorder known as thrombosis with thrombocytopenia syndrome, or TTS.
COVID-19 infection itself is also linked to thromboses, or blood clots, in some patients.
What are the key advantages and disadvantages of viral vector vaccines?
Viral vector vaccines are based on well-established technology and tend to trigger a strong immune response—often providing robust and long-lasting protection with just one dose.
However, viral vector vaccines can also be quite complex and costly to manufacture.
In very rare instances, people can develop a level of immunity to the vector virus itself, reducing the response to and effectiveness of the vaccination.
mRNA vaccines – What they are, and what they are not
Protein subunit vaccines – What they are, and what they are not
